Yarrow is the name given to a number of subspecies of Achillea millefolium that have a virtually identical appearance but different numbers of chromosomes. The taxonomy of Achillea millefolium is inconsistent, and subspecies as well as related species are variously categorized as Achillea millefolium. Subspecies of yarrow are found in many regions, particularly in eastern, southeastern, and central Europe.

Legend has it that the botanical grouping, or genus, of yarrow was named Achillea because Achilles, the Greek mythical figure, used yarrow to staunch the bleeding wounds of his soldiers. Popular in European folk medicine, yarrow has traditionally been used to treat menstrual ailments and bleeding hemorrhoids. This plant is a distant botanical relative of German (or Hungarian) chamomile and English chamomile, and it has some of the same chemical constituents found in the two chamomiles. As in the case of chamomile, yarrow is a common herbal remedy for bloating, flatulence, and mild gastrointestinal cramping.

Chamomile and yarrow belong to the Asteraceae, or daisy, family. Plants in this family contain a bluish-colored essential oil that owes its color to the presence of intensely blue azulene derivatives. The azulene constituents and other active principles in the volatile oil of yarrow have anti-inflammatory effects.

While the chemistry of various subspecies of yarrow has not been fully elucidated, some of the therapeutic claims for this plant have been documented. Pharmacological studies indicate that yarrow has diaphoretic (perspiration-promoting), antipyretic, hypotensive, astringent, diuretic, and urinary antiseptic activity.

Yarrow grows as a simple, erect, and hairy stem that reaches a height of 0.1 to 1.5 m. It flourishes in a sunny and warm habitat, and is frequently found along meadows and roadsides, as well as on dry, sunny slopes. The entire plant (with the exception of the fruit) is draped in white, silky appressed hairs, which gives it a white hairy-like appearance. Growing from underground runners are tough, angular, horizontal stems that bear flowers.

Yarrow blooms between June and September. The flowers are typically white, but either pink or pale purple infloresences are common in species found in mountain areas. The flowers are composite and densely arranged in flattened, umbel-like clusters. The leaves are alternate, lanceolate, and multi-pinnate with a feathery appearance.

Part Used/Pharmaceutical Designation

• Flowers (flowerhead)
• Whole herb
• Above-ground parts

Volatile oil (0.2% to 1.0%, components are variable depending on strain/subspecies; e.g., chamazulene [blue, 6% to 19%, maximum 40%], camphor, beta-pinene, 1,8-cineole, carophyllene, alpha-thujone). Sesquiterpene lactones (primarily guaianolides, e.g., achillicin, achillin, millefin, millefolide; sesquiterpenes may be converted to chamazulene [proazulenes] through steam distillation); flavonoids, acids, alkaloids/bases (e.g., betonicine, stachydrine [pyrrolidine]), polyynes, alkamids, tannins, unknown cyanogenetic compound, sugars.

Commercial preparations are made from both the herb (fresh or dried above-ground parts) and dried yarrow flowers of Achillea millefolium. Plant material is harvested during the flowering season and then dried. Essential oil preparations should not be stored in synthetic containers. Yarrow drug contains volatile oil which must be protected from light and moisture. Yarrow is a component in multi-herbal formulations of two gastrointestinal teas listed in the German Standard Registration of phytopharmaceutical products.

Traditional uses:

• Internal: cold, fever, measles, essential hypertension, cerebral and coronary thromboses, amenorrhea, dysentery, diarrhea; whole plant decoction used for bleeding piles, kidney disorders
• External: wound healing, skin inflammations; sitz (partial) bath for pain and cramps in lower female pelvis, liver ailments

Conditions: used as diaphoretic, antipyretic, anti-inflammatory, spasmolytic, hemostatic, hypotensive, emmenagogue (induces menstruation), choleretic (stimulates production of bile by the liver), cholagogue (stimulates flow of bile to duodenum), antibacterial astringent, antispasmodic, gallbladder therapeutic

Clinical applications: loss of appetite, dyspeptic (digestive) complaints, liver and gallbladder complaints, hypertension, menorrhagia, irritable bowel disease, influenza

In in vitro experiments, ethanolic extracts of yarrow showed moderate antibacterial activity, with the sesquiterpene lactone fraction also exhibiting antibacterial properties. In in vivo studies, an aqueous extract of true yarrow produced anti-inflammatory activity in paw edema models of mouse and rat, and had topical anti-inflammatory activity in rabbits. In general, anti-inflammatory properties have been associated with azulenes, the major component of the essential oil.

Yarrow extract administered to mice at a dose over twice that needed for anti-inflammatory effect showed diuretic activity. The diuretic action has been attributed to terpinen-4-ol. The essential oil also yielded CNS depressant activity by reducing spontaneous activity of mice and by lowering body temperature of rats. In test animals, the volatile oil from yarrow prolonged barbiturate-induced sleep and inhibited pentetrazole-induced convulsions.

Another chief constituent, achilleine (0.5 g/kg IV) displayed hemostatic effects by reducing blood-clotting time by 32% in rabbits for 45 minutes and was devoid of observable toxic side effects. Azulene compounds in the flavonoid-containing fraction of yarrow may account for the antispasmodic activity of this plant on isolated rabbit intestine. Other research suggests that azulene-related constituents such as chamazulene and prochamazulenes also have anti-inflammatory properties. Additional investigations reveal that the basic fraction of yarrow extracts (containing alkaloid/base) exhibited antipyretic and hypotensive effects, while the sesquiterpene lactone fraction elicited cytotoxic action.

• Dried herb: 1 to 4 g tid as infusion or capsules
• Extract (1:1, 25% ethanol): 1 to 4 ml tid
• Tincture (1:5, 40% ethanol): 2 to 4 ml tid
• Yarrow flowers, or equivalent preparations: 3 g per day as infusion
• Sitz baths: 100 g yarrow per 20 liters (5 gal) of water.

Although yarrow is described as nontoxic, it can cause allergic reactions in sensitized individuals.

While yarrow is reportedly free of adverse side effects when administered in designated therapeutic dosages, some individuals have allergic reactions to this plant. Yarrow has a potential for sensitization.

Yarrow should be avoided during pregnancy since it has abortifacient properties and affects the menstrual cycle. _{Lactating women should avoid excessive use.}

No clinically significant interactions between yarrow and conventional medications are known to have been reported in the literature to date, including the German Commission E monograph (Blumenthal 2000).

Yarrow is listed in the General Sale List (GSL) of approved therapeutic agents in the United Kingdom. It is listed as an approved herb by the German Commission E, and accepted in Belgium and France for specific indications. The Council of Europe approves yarrow as a natural source of food flavoring (category N2) but prohibits certain concentrations of alpha and beta thujone in foods and alcoholic beverages. In the United States, yarrow is not approved as a food additive, and alcoholic beverages containing yarrow must be thujoid-free.

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